linux-imx

/*

 *

 * Driver for ST M41T93 SPI RTC

 *

 * (c) 2010 Nikolaus Voss, Weinmann Medical GmbH

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

​

#include <linux/bcd.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/platform_device.h>

#include <linux/rtc.h>

#include <linux/spi/spi.h>

​

#define M41T93_REG_SSEC         0

#define M41T93_REG_ST_SEC       1

#define M41T93_REG_MIN          2

#define M41T93_REG_CENT_HOUR        3

#define M41T93_REG_WDAY         4

#define M41T93_REG_DAY          5

#define M41T93_REG_MON          6

#define M41T93_REG_YEAR         7

​

​

#define M41T93_REG_ALM_HOUR_HT      0xc

#define M41T93_REG_FLAGS        0xf

​

#define M41T93_FLAG_ST          (1 << 7)

#define M41T93_FLAG_OF          (1 << 2)

#define M41T93_FLAG_BL          (1 << 4)

#define M41T93_FLAG_HT          (1 << 6)

​

static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data)

{

    u8 buf[2];

​

    /* MSB must be '1' to write */

    buf[0] = addr | 0x80;

    buf[1] = data;

​

    return spi_write(spi, buf, sizeof(buf));

}

​

static int m41t93_set_time(struct device *dev, struct rtc_time *tm)

{

    struct spi_device *spi = to_spi_device(dev);

    int tmp;

    u8 buf[9] = {0x80};        /* write cmd + 8 data bytes */

    u8 * const data = &buf[1]; /* ptr to first data byte */

​

    dev_dbg(dev, "%s secs=%d, mins=%d, "

        "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",

        "write", tm->tm_sec, tm->tm_min,

        tm->tm_hour, tm->tm_mday,

        tm->tm_mon, tm->tm_year, tm->tm_wday);

​

    if (tm->tm_year < 100) {

        dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n");

        return -EINVAL;

    }

​

    tmp = spi_w8r8(spi, M41T93_REG_FLAGS);

    if (tmp < 0)

        return tmp;

​

    if (tmp & M41T93_FLAG_OF) {

        dev_warn(&spi->dev, "OF bit is set, resetting.\n");

        m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);

​

        tmp = spi_w8r8(spi, M41T93_REG_FLAGS);

        if (tmp < 0) {

            return tmp;

        } else if (tmp & M41T93_FLAG_OF) {

            /* OF cannot be immediately reset: oscillator has to be

             * restarted. */

            u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;

​

            dev_warn(&spi->dev,

                 "OF bit is still set, kickstarting clock.\n");

            m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);

            reset_osc &= ~M41T93_FLAG_ST;

            m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);

        }

    }

​

    data[M41T93_REG_SSEC]       = 0;

    data[M41T93_REG_ST_SEC]     = bin2bcd(tm->tm_sec);

    data[M41T93_REG_MIN]        = bin2bcd(tm->tm_min);